1. Field of Invention
The invention relates to an ink-jet recording apparatus that ejects ink to record on a recording medium.
2. Description of Related Art
Ink-jet recording apparatuses are typically provided with actuators formed by piezoelectric elements or heating elements, and eject ink selectively by deforming the piezoelectric elements or by locally heating ink to a boil using the heating elements. Ink is supplied, via a tube or directly from an ink cartridge, to a plurality of actuators through an ink passage. A filter is typically provided in the ink passage to remove foreign matter and air bubbles from the ink flowing into the actuators.
Occasionally, in such ink-jet recording apparatuses, a number of actuators are simultaneously driven to eject ink, or ink is sucked while a number of nozzles are covered with a cap to perform a recovery operation. In such cases, the ink passage should have a cross-sectional area appropriate for supplying a large amount of ink to the actuators.
A filter typically has very small openings in its lattice frame. Ink is supplied through the filter to the actuators. Thus, the total area of the openings of the filter should be large enough to allow a large amount of ink to be supplied at any given time. The total area of the openings should be larger than the cross-sectional area of the ink passage.
Recently, high-resolution and multilevel gray-scale printing has become popular. As the demand for this printing grows, a number of actuators are arranged in a single head, and the diameter of each nozzle is made to be extremely small. In some cases, a plurality of ink droplets are continuously ejected to form a dot. Further reducing the size of openings of the filter is advantageous to remove smaller foreign matter and air bubbles, while further increasing the total area of the openings of the filter is advantageous to allow a larger amount of ink to be supplied at any given time. To achieve these advantages, the ink passage should be enlarged on the upstream and downstream sides of the filter.
By increasing the velocity of flow of ink passing through the filter in a structure wherein ink is sucked with a number of nozzles that are covered with a cap, when ink is forcibly ejected under high pressure applied from an ink source side, or when all actuators are simultaneously driven to perform flushing (hereinafter, these operations are generically referred to as xe2x80x9crecovery operationsxe2x80x9d), air bubbles are forced to pass through the filter and are discharged through the nozzle.
However, when the total area of the filter is large, the velocity of flow of ink is reduced on the upstream side of the filter, resulting in a deposition of air bubbles generated in the ink on the upstream side of the filter. Air bubbles deposited on the filter reduce the effective area of the filter. As a result, ink supply becomes insufficient, and faulty ink ejection is caused when a number of actuators are simultaneously driven or when actuators are continuously driven to perform printing.
According to the invention, air bubbles on the upstream side of a filter are effectively discharged, and excellent ink ejection can be maintained for a long time.
In the invention, a partition member is provided to define a path of ink passing through a filter.
In this configuration, the path of ink passing through the filter can be narrowed, and thus the velocity of flow of ink can be increased when recovery operations are performed as described above, or when a number of actuators are simultaneously driven. Consequently, air bubbles in the ink are deformed to easily pass through the filter. Then, air bubbles are discharged through the actuators to the exterior of the device. Accordingly, faulty ink supply due to air bubbles is prevented, and excellent ink ejection can be maintained for a long time.
The partition member preferably includes a rib extending parallel to the filter. Ink is guided along the rib. Even a partition member that has a complex shape can be easily molded from a resin. Further, a peripheral wall may be provided so as to enclose the periphery of the filter. The peripheral wall and the partition member cooperate to guide the ink, through the effective use of the entire surface of the filter, and produce an ink flow effectively passing over the entire surface thereof.
When the partition member is configured so as to be appropriately spaced from the peripheral wall, a rapid ink flow is effectively produced and guided in a circumferential direction of the filter. Further, when the partition member is configured so as to extend in a spiral manner, the ink is guided to turn from the periphery to the center of the filter or from the center to the periphery thereof. Accordingly, a rapid ink flow is effectively produced over the entire surface of the filter.
The partition wall may include two parallel ribs extending substantially from the center of the filter toward a direction approaching the peripheral wall. In this configuration, ink supplied to the center of the filter is guided along the peripheral wall, or ink supplied to the peripheral wall side is guided to the center of the filter. Thus, an ink flow is effectively produced over the entire surface of the filter.
When the partition member includes a plurality of ribs disposed parallel to each other and each rib is spaced, at at least one of its ends, from the peripheral wall, the ink is guided along the ribs in a zigzag manner. Accordingly, an ink flow can be effectively produced over the entire surface of the filter.
It is more preferable that a guideway is provided so as to supply the ink in a direction parallel to the filter surface. Such a guideway allows the ink to be supplied over a wider area of the filter and an ink flow can be effectively produced along the filter surface. In this case, the guideway may have a curved surface that redirects the ink gradually from a direction intersecting the filter surface to a direction parallel thereto. Even when the ink passage above the filter extends substantially perpendicularly to the filter surface, the ink flow is redirected by the guideway immediately before the ink is supplied to the filter and, as a result, the ink flows along the filter surface. Accordingly, the ink is supplied over a wider area of the filter without being concentrated into a certain portion thereof.
When the guideway extends parallel to the filter surface, the ink flows along the filter surface to be supplied over a wider area of the filter. Further, when the guideway extends parallel to a tangent to the periphery of the filter, a rapid ink flow is produced that passes along the periphery of the filter and along the filter surface.
In this configuration, a rapid ink flow is produced to pass in a spiral manner from the periphery to the center of the filter. Consequently, air bubbles in the ink are deformed to pass through the filter, and then are discharged to the exterior of the device.
The peripheral wall that encloses the filter may be formed to be round, continuous and integral with a part of a wall defining the guideway. When the width of the guideway is less than the radius of the peripheral wall, the velocity of flow of ink in the guideway is increased. Thus, the ink flows more effectively and rapidly in a spiral manner.
Further, the ink passage maybe a space defined by joining two members, which extend parallel to a direction of flow of ink, so as to face each other. A port connected to the recording head is integrally formed with one of the two members and covered with the filter, and the partition member is formed integrally with the other of the two members. When the two members are joined to each other, the partition member comes into contact with, or alternatively is disposed close to but not in contact with, the filter. By simply joining the two members so as to sandwich the filter, the ink passage and the partition member can be easily formed.